Common temperature control methods of PVC sheet extrusion production line

1. Discrete instrument panel
According to the requirements of the manufacturing process, each zone is controlled by the method of temperature controller + intermediate relay (electric heater) + vacuum solenoid valve (air-cooled or water-cooled). The effect of this kind of control scheme is not bad under static conditions, but under dynamic conditions (normal operation), even the air-cooled type is only average, let alone water-cooled heat dissipation equipment, and the PVC board The discrete structure of the extrusion production line is also not conducive to the implementation of the heating current monitoring function (because each circuit needs an independent voltage transformer). In addition, the application of several temperature controllers makes the entire power circuit structure more complicated. It is more and more complicated, and installation, wiring and adjustment are more inconvenient. On the one hand, it increases the labor cost, and on the other hand, it also increases the possibility of problems.
2. PLC control
The soft PID control module embedded in the PLC is used for temperature control. Its processing speed exceeds the company's discrete instrument panel, and the equipment failure rate is also low. Due to the limitations of PLC in floating-point calculation functions, its effective operation effect is not even as good as that of a single meter (because of its relatively simple PID function), and this solution is not compatible with the heating current monitoring function.
3. Dedicated control loop module
In order to make up for the shortcomings of the first two schemes, more and more special-purpose PID control modules have been used in recent years. Use special closed-loop control multi-control loop modules such as MLC9000 to centralize the transportation temperature control, each control module is controlled by 2-4 channels, which simplifies installation, adjustment and wiring, but the essence of this control module is to combine several single meters Revocation shows that integration into one control module does not substantially improve the optimization algorithm.